In an inkjet recording device including an ink circulation type inkjet head, ink circulates without staying in the vicinity of nozzles. Thus, deterioration of the ink and precipitation of a color material can be prevented, and ejection stability of the ink can be improved. In recent years, the inkjet head and an ink circulation device can be integrally connected and unitized, and compactification is achieved. However, in order to realize miniaturization of the device, in a case of adopting a piezoelectric pump as an ink circulation pump, small bubbles generate easily in a pressure chamber of the piezoelectric pump of which pressure is fluctuated at high frequency. The bubbles contained in the ink are circulated together with the ink in the inkjet head and the ink circulation device.
If bubbles enter the ink pressure chamber in the inkjet head, pressure for ejecting an ink droplet is decreased, and ejection failure results. In order to prevent this undesired result, an air trap filter for catching the bubbles contained in the ink is arranged at an ejection side of the piezoelectric pump in the ink circulation device. In this way, bubbles in the ink are accumulated in a space at the upstream side of the filter.
However, the volume of the space at the upstream side of the filter becomes small as well when miniaturizing the device, the bubbles trapped in the filter readily accumulate at the upstream side of the filter in a relatively short time.
If air is accumulated at the upstream side of the filter, a contact area of the ink and the filter becomes small, and a flow rate per unit area passing through the filter is increased. As a result, pressure loss of the filter becomes large, and the circulation flow rate of ink is reduced. Furthermore, if the contact area of the ink and the filter becomes small, the pressure loss of the filter becomes large. If the pressure at the upstream side of the filter exceeds bubbles point pressure which is generated when air passes through the filter, the bubbles in the ink passes through the filter together with the ink, the ejection failure due to the bubbles is generated.